Die casting mold breather



Oct. 29, 1963 H. R. BUCY DIE CASTINGVMOLD BREATHER 2 Sheets-Sheet 1Filed May 20, 1959 FIG.

INVENTOR.

HARRY R. BUCY AHorney H. R. BUCY 3,108,339

DIE CASTING MOLD BREATHER Oct. 29', 1963 Filed May 20, 1959 2Sheets-Sheet 2 S shlllllfi J0 J0 Afiorney United States Patent 3,108,339DIE CASTING MOLD BREATHER Harry R. Buoy, 625 S. Glenwood Place, Burbank,Calif. Filed May 20, 1959, Ser. No. 814,515 14 Claims. (Cl. 22-152) Thisinvention relates to pressure die casting and more particularly to animprovement in the construction of the molds or dies whereby the flow ofmetal into and throughout the mold cavity is controlled and facilitatedby the improved means for the expulsion of air from the mold cavity bythe injected molten metal.

In the formation of die casting dies, the practice has been to formnarrow vents comprising wide, shallow grooves having a depth of, say,.005 or less in the meeting faces of one or the other of the diesconstituting a mold, said grooves leading from the mold cavity to theoutside of the dies. Reference to such current practice will be found inthe book entitled Die Casting by Charles 0. Herb, published by TheIndustrial Press, copyright 1952, Second Edition, page 70, and in thebook entitled Die Casting by H. H. Doehler, published by McGraw-HillBooks, copyright 1951, at page 84. Thus, venting has been possible onlyat the parting line of the dies. There have been proposals to vent thedies elsewhere by openings containing porous metal plugs but these soonfill with the molten metal.

Upon charging the mold cavity with molten metal, the air is forced outof these vents and if any air should be trapped in the mold cavity, aporous casting results. The molten metal extrudes part way into thevents before becoming chilled sufiiciently to prevent further movementand thus seals the vents so that the final casting pressure can beapplied. Obviously, if the vent were so wide as not to allow thisself-sealing action, the die would be useless. The metal thus enteringthe vents leaves a fin on the casting which then must be removed.

These shallow vents often become at least partially closed either by themetal soldering itself to the groove or vent surface or by incrustationof carbon from any lubricant that may be applied to the dies. This,then, adds to the back pressure of the expelled air and results inporous castings. The removal of such metal or incrustation from thesevent grooves without increasing the depth thereof to an extent unable tostop the molten metal from being expelled therefrom and without marringthe cavity surface is a delicate and costly operation.

In eiforts thus to remove the air from the mold cavity in advance of theincoming metal, many proposals have been made to enclose the meetingfaces of the die with a vacuum means so that, in theory at least, all ofthe air or at least a significant part thereof will have been removedfrom the mold cavity before the shot is made. These proposals fail totake into account the fact that if the die vents should be partly orwholly plugged, the mold cavity may not have been sufiiciently evacuatedto produce a non-porous casting. Obviously, these vacuum devices make itimpossible to determine whether or not the die vents are operatingproperly and the operator can only hope that the die or mold cavity isproperly evacuated at the time he causes the metal to be injected.

The present invention takes into account all of these prior artdifiiculties and shortcomings and is directed to means for permittingthe expulsion of air from the mold cavity at points other than the diemeeting faces. To distinguish from the vents commonly employed on themeeting faces of the dies heretofore employed, the orifices employed inthe present invention for allowing air to be expelled from the moldcavity will be designated as breathers since air actually movestherethrough both 3 1%,339 Patented Oct. 29, I963 into and out of themold cavity as will hereinafter be appreciated in connection with thedescription of the manner of use of these breathers. Moreover, as willalso be explained in detail as the description of the inventionproceeds, by choosing the position in the die for the various breathersand controlling the rates of air flow through individual breathers, thedirection of flow of the molten metal through the mold cavity can bemade to follow a pattern which will insure the filling of the cavity inthe least possible time, wherefore, the danger of meeting streams of themetal in the die forming cold shuts will be leliminated.

An object of this invention is to provide an improved mold breatherstructure to enable air and gases to be expelled from the mold cavity atone or more points other than the meeting faces of the dies constitutingthe mold.

Another object of this invention is to provide an improved breathereffective to permit the expulsion of air and gases from the mold cavityby the entry of the molten material into a die casting mold whilepreserving the integrity of the meeting faces of the dies forming themold cavity.

Still another object of this invention is to provide a mold breatherwhich is adaptable for location in areas of a mold cavity which would beunsuitable or impossible for vents used heretofore.

Still another object is to provide a mold breather which may be employedto control the amount of back pressure exerted by the expulsion of airfrom the mold cavity incident to the entry of the molten metal withreduction of the possibility of porosity of the casting.

Still another object is to provide an improved mold having a cavity soconstructed that the metal or material to be cast therein will quicklyflow to all parts of the mold and which the resulting casting ischaracterized by an absence of flash at the parting line of the diesconstituting the mold.

A further object is to provide a mold breather which will permit changesto be made in the rate of air flow therethrough with resultant changesin the flow pattern of the molten material injected into the moldcavity.

These and other objects of the invention not specifically set forthabove will be readily apparent from the accompanying description anddrawings of certain presently preferred embodiments of the invention andin which:

FIGURE 1 is a fragmentary sectional view taken on a plane passingthrough the mold cavity portion of a pair of die casting dies showingdetails of two mold breathers of this invention.

FIGURE 2 is a perspective view of an untrimmed casting taken from a moldcavity comprising the dies shown in FIG. 1 and using the mold breathersof this invention; the overflow metal cast in the mold breathers beingshown in phantom.

FIGURE 3 is a fragmentary view of the cavity surface of the diecomprising the lower section of the mold shown in FIGURE 1.

FIGURE 4 is a view of the platen engaging surface of the top die of themold of FIGURE 1 showing means for attaching a separate vacuum line toeach of two breathers of the present invention for purposes hereinafterto be described.

FIGURE 5 is an alternative configuration of the die surface of FIGURE 4showing means for attaching a single vacuum line.

FIGURE 6 is a sectional view of a mold in which the breather of thisinvention extends directly from the casting.

FIGURE 7 is a sectional view of a vacuum device suitable for the new andnovel use of vacuum employed in the present invention.

Heretofore, the only function of a mold vent has been to allow air andgases to escape from the cavity of a die or mold as the metal or othermaterial to be cast is injected into the mold. However, if the capacityof the vents for air flow is too limited, the air tends to develop aback pressure in direct relation to the volume of metal injected withina given time. This back pressure may result in some of the air beingentrapped by the cast metal. One function of the novel breatherconstruction of the present invention is to reduce and conrol this backpressure and thereby minimize the possibility of porosity in thecasting.

The construction of the breather of the present invention allows rapidbut controlled escape of air and gases but, like the vents heretoforeused, it is restrictive of the molten casting metal by reason of theviscosity thereof and similarly prevents the flow of metal therethroughto permit the final injection pressure to be imposed before the metalcan escape from the breather.

Additionally, the breather construction of the present inventionpossesses advantages not heretofore available in the die casting art.First, it provides a means for predetermining the fiow pattern of theinjected metal throughout the mold cavity. Second, it affords a meansfor determining that the metal can enter the mold cavity withoutdeleterious back pressure opposition. Third, it makes unnecessary thecomplex full vacuum casting machines and processes heretofore employedin an effort to achieve non-porous castings.

Referring now to FIGURE 1, there is shown a fragmentary cross section ofa mold suitable for casting a shallow, rectangular, open-sided, box-likeobject having an opening in one wall such as shown in FIG. 2. 1n theformation of this casting, two breathers of the present invention areemployed. FIGURE 2 is a perspective view of the casting made by means ofthe mold of FIG- URE 1. The material cast in the novel passages leadingto the breathers is shown by the dotted outline 56 and 57. This surplusmaterial is trimmed off at points 58-62, after the casting is removedfrom the mold. In one instance, a pad surplus metal has been cast inpocket 63 having a circular shape whereas the other breather projectsfrom a cruciform pocket 64. It should be understood that anyconfiguration of pocket suitable to the casting involved may beemployed, and, as will be shown later, such pocket may be dispensed withaltogether if the form of the casting permits.

In conventional die casting machines, the mold is composed of two diesections which separate when the machine is opened to permit removal ofthe casting. These sections are carried by two relatively movableplatens of a die casting machine as is well known to those skilled inthe art. The use of the terms upper and lower as applied to the drawingswill be understood to relate only to the drawings and it will beunderstood that the dies shown may be employed either in vertical orhorizontal die casting machines. Looking now at FIGURE 1, the mold ventis formed by dies 1 and 2 which define the mold cavity 3. The upperplaten of the die casting machine is shown at 4 and the die supportingblock for the lower die is shown at 4'. Molten metal is injected fromthe shot cylinder of the machine through sprue hole 5. Gates or bleedpassages 6 for the molten metal can be located at a number of pointsaround the edge of the mold cavity so that during die casting underpressure, the metal may be forced through cavity 3 towards overflowpockets 7 and 8. This arrangement will insure explusion of air fromcavity 3 and will also insure that the portion of the cavity occupied bythe casting, per se, is completely filled With metal. It should beunderstood that overflow pockets may or may not actually be required,this being determined by actual molding conditions.

As above mentioned, die casting mold cavities have heretofore beenvented to atmosphere through one or more very small passages extendingfrom the mold cavity to the edges of the dies, this being usually adistance of not less than about 1 /2". Thus, the air expelled from themold cavity is subjected to high resistance through this long passage orvent. Also, as has been previously mentioned, the small cross-sectionalarea of the vent would tend to cause any metal which entered it tosolder to the mold sections. This soldered metal is very difiicult toremove, and if not removed, will plug the vent and cause malfunctioningduring succeeding casting operation.

This difliculty is overcome by the novel breather of the presentinvention wherein the meeting faces of the dies are uninterrupted byvents and means is provided to afford escape passages for expelled airthrough one or the other of the dies.

Specifically, the breathers of the embodiment of the invention shown inFIGS. 1 through 5 comprise frustoconical bores 12 and 13 disposed withthe larger ends thereof communicating with the portions of the diecavity forming the centers of the casting portions 63 and 64 and thenceextend to a point inwardly from the outer face of the die and thencecontinuing to said outer face as straight bore portions 12' and 13 ofthe same diameter as the smaller diameters of said frusto-conical bores.Cooperating with said breather bores are core members it) and 11 carriedby the die 2 and disposed to enter said bores; said core members havingfrusto-conical portions 10' and 11', respectively, beginning at theplanes of the cavity surfaces in the die 2 from which they project andterminating at the plane of termination of the bore with which theyrespectively enter, said bores thence continuing into the straight boreportions 12 and 13 with straight cylindrical portions 10" and 11",respectively. The angle of the frusto-conical portions 10 and 11 of thecores 10 and 11 is slightly less than the angle of the frusto-conicalbores with which they cooperate, thus forming hollow, frusto-conicalcavities 16 and 17 and the clearance between the cores and the bores atthe smaller ends thereof forms breather passages 14 and 15 of suchlimited clearance that air can freely flow therethrough but which, likethe prior art vents, will not permit the molten metal to passtherethrough. Thus, as the molten metal enters the mold cavity drivingout the air therefrom, it will also enter the breather cavities as faras the clearance between the bores and cores will permit and willeventually seal itself off in a usually ragged edge as indicated at theouter ends of the portions 56 and 57 shown in FIG. 2. As the metal coolsand congeals it will shrink on to the cores 10 and 11 so that when thedies are separated, due both to the shrinkage of the metal to the coresand to the fact that the metal entering the breather cavities is ofgradually increasing thickness toward the mold cavity, together with thefact that the faces of the tapered bores present a most favorable draftangle, all of the metal which has entered the breather cavities willusually pull out completely clean from the breather bores. When thecasting is removed from the mold, the surplus portions 63 and 64together with the portions 56 and 57 thereof which have entered thebreather cavities are removed by shearing them from the casting at thevarious gates 6. It is to be noted particularly that the metal does notenter and seal off any breather cavity until the portion of the moldcavity served by that breather has been completely filled.

It will be noted that the restricted portions of the breather passagesare very short, thus appreciably reducing the frictional resistancethereof to the escaping air. Moreover, since they are circular, they canbe of much greater capacity than is possible with the prior art ventsformed in the meeting surfaces of the dies, it being noted that abreather passage of /2" diameter is equivalent to a die surface vent 1/2" wide. Still further, the

various breathers for a single casting may be of different diameters andof different clearances so that the optimum sequence of metal flowthrough the various portions of the mold cavity can be predetermined,the metal first flowing toward the breather having the greater capacityfor air escape and lastly toward the breather having the more limitedrate of air flow therethrough. When all of the breathers are filled withmetal and are sealed by the inflowing metal, the final casting pressurecan be applied to achieve the desired homogeneity in the casting. In theconstruction of dies, the usual ejecting pins as at 18 are supplied toeject the casting from the portion of the mold cavity in the die inwhich the casting is retained after the dies are separated and, in thecasting here shown, two of the ejector pins engage the disc like surplusportions 63 formed in the pocket 7, another engages a wall surface ofthe casting, while still another engages one of the arms of thecruciform surplus portion 8 as thus shown in FIG. 1. The number andlocation of such ejector pins is such as best suits the particularcasting.

Looking now at FIGURE 6 there is shown a sectional view of a die forcasting a ring-like object and which employs the breather core as aportion of the molding surface. In this embodiment of the invention, thewalls of the mold cavity are defined by upper die 20, lower die 21, andbreather core 22. The core 22 is carried by the die 21 and thenceextends across the mold cavity. Beyond the mold cavity, it is providedwith a tapered portion 22 disposed coaxially within and spaced from thewall surface of the frusto-conical breather bore 27. The tapered wallsof the core and bore diverge from a narrow gate portion 27' at thejuncture with the mold cavity and then converge to provide a narrowbreather orifice 28 between them formed between the straight end portion29 of the core and the corresponding straight portion 29 of the breatherbore. The molten metal is injected through sprue 23 formed by the upperand lower dies. The metal fills mold cavity 24 and then fills the ventcavity 25 to the extent permitted by the approach of the core and ventsurfaces toward each other in the formation of the breather orifice 28,the air in the mold cavity being, of course, expelled through thebreather as the metal fills the cavity. Removal of the casting from theseparated mold sections is facilitated by ejection pins 30 slidinglymounted in holes 31 in the die 2. Thus this embodiment is similar tothat first described above, the principal difierence being that wherethe form of the casting permits, and overflow pocket can be dispensedwith.

By lowering the back pressure of the air within the mold cavity, it ispossible to remove more air within a given time than is possible withprior mold vents. This results in a further advantage in that thepossibility of porosity in the casting caused by trapped air is, for allpractical purposes, eliminated.

When the mold sections are separated, carbon or other extraneousmaterial can be easily wiped or otherwise removed from the core andbreather bore surfaces without the possibility of damage to critical diesurfaces. Normally, any soldering of metal would collect on the core,rather than on the walls of the aperture, because of the thickness ofmetal thus forming. In the event that during molding the die is notsecurely locked up, it may be possible for metal to completely fill theopening beyond the bleed passage. Should this occur, this surplusmaterial can be easily removed by simply punching out the cast materialfrom the aperture through the back of the upper die section.

Many attempts have heretofore been made in the art of die casting toreduce the porosity of castings by exhausting the air and gases withinthe mold cavity by a vacuum means which isolates the mold cavity fromatmospheric pressure while the metal is injected into the mold cavity.The present invention employs a vacuum means which could be so employed,if desired, but which has the primary function of making it possible todetermine before each shot that each individual breather is functioningproperly and is not even partially plugged up. Obviously, if there is nopossibility that air will be trapped in the mold cavity, the need forexpensive vacuum equipment is dispensed with. In those prior art moldsin which the entire mold is isolated and subjected to vacuum, there isno possibility of checking the individual vents. It is, of course,necessary in all cases that upon filling the die with metal, that themetal seal off the breathers or vents for application of such pressureto the molten metal in the cavity as the die casting machine imposes.

The air escaping from the breathers of the present invention must beconducted to the exterior of the die without obstruction and since thebreathers emerge at the face of the die which is fixed to the machineplaten, grooves are formed in the outer or platen engaging face of thedie and extend laterally from the breather bores 12 and 13 to combinewith the adjacent face of the platen 4 to form air conducting passages32 and 33. If no vacuum or breather operation test means is to beemployed, these grooves can continue to the edge of the die. To attachthe vacuum means of this invention to the breathers of this invention,the passages 32 and 33 are terminated short of the edges of the die andare thus sealed off at the points identified as 34 and 35 and vacuumlines are separately attached thereto. In a typical installation, asshown in FIGS. 3 and 7, a hole 36 may be drilled inward from the bottomof the groove 32 and a second hole 37 may be drilled to connect to thefirst hole from the outside edge of the die. This second hole 37 may beadapted for communication with a vacuum line 38 in a member 39 fixed tothe side of the die 1.

There is shown in FIGURE 4 a top View of an upper die section which hasbeen adapted for use with two vacuum lines. The top of apertures 12 and13 communicate with passages 32 and 33 which may have as their upperboundary the surface of the upper platen 4 of the die casting machine.These passages connect with holes 36 and 40, which in turn connect withvacuum lines in members 39 and 41. As is shown in FIGURE 5, a singlevacuum line member 42 may serve to exhaust two breather apertures 12 and13 via a linking passage 43 formin a continuation of passage 32. Othervariations will become apparent to one skilled in the art from theteaching of this invention.

A vacuum applied to line 38 during injection of the molten metal willpermit the air and gases to be more readily expelled by the incomingcasting metal. The resulting reduction in back pressure will furtherreduce the possibility of porosity in the casting.

When used to assist the flow of metal in the mold cavity, the vacuum isapplied when the casting metal is in the shot cylinder of the diecasting machine but before the plunger or a piston of the shot cylinderstarts to inject the material through the sprue hole into the mold. Thismaintains a reduction of the atmospheric pressure within the cavity eventhough some air may still enter through the shot the ejection pinclearance in the mold or between the juxtaposed faces of the dies. Theuse of a vacuum to aid in more rapidly exhausting air from the moldcavity will also permit a larger casting to be made before the metalchills. Furthermore, this will permit the casting of structures havingthinner wall sections and more detail than has been readily practicalheretofore.

By means hereinafter to be described, the application of a vacuum to thebreather of the present invention may be used for checking the properoperation of the vents to assure that they are not plugged. A vacuumgage connected to the vacuum line will indicate a predetermined lowerdesired vacuum when the breather is correctly functioning and a highervacuum indicated on the gage discloses that the breather is at leastpartially obstructed so that remedial steps can be taken before the shotis made.

In order to provide the vacuum suitable for exhausting the air from thedie cavity, in the manner discussed above, a jet-top type of vacuumproducing device such as generally indicated at 44 in FIG. 7 may beemployed, it being understood that the body of said device may be thebody indicated by any of the numerals 39, 41 or 42 in FIGS. 4 and 5, andthe numerals 38 in FIG. 3 and 46 in FIG. 7 indicate identical passages.This is a well-known mechanism, sometimes referred to as a vacuum-gunand in the illustrated embodiment employs the venturi-like action of ahigh velocity jet of air delivered into the inlet end of a dischargenozzle which affords communication between a passage connected to thebreather and the atmosphere.

Specifically, in the embodiment disclosed in FIG. 7, the body member 44includes a passage 49 connected by a fitting 48 and the line 47 to asource of compressed air, it being understood that the line 47 will havevalve means to permit and prevent the flow of compressed air to thedevice. The body 44, further, includes a second passage 46 extendingparallel to the passage 49; said passage being in communication with thebreather exhaust passage 37 at one end and with a fitting 45 mounting avacuum gage 53 at the other end. The body 44 is provided with a seriesof large threaded bores 45 extending into the passage 46 with theiraxial lines disposed parallel to each other and in a plane containingthe axial lines of the parallel pas sages 46 and 49. Threadedly engagingsaid bores are the inlet ends of discharge nozzles 55, the outer ends ofwhich are open to atmosphere. Disposed in axial alignment with one eachof the bores 45 is one each of an equal number of branch passages 50extending between the passages 49 and 46; each of said branch passagesat the juncture with the passage 46 terminating in a threaded portion50' and a counterbore 50"; said counterbores being not larger than theinternal diameter of the threaded bores 45. Threaded into the portions50' are the ends 52 of jet nozzles 51, the opposite ends of which aresmaller than and project into the axially aligned inlet ends of thedischarge nozzles 55. Externally, each of the jet nozzles is providedwith a hexagonal section 51' disposed in the eounterbore 50". It will benoted by this arrangement, the jet nozzles are mounted in their boresthrough the bores 45. The high velocity jet of air entering eachdischarge nozzle will draw air from the mold cavity through theconnection thereof with the breather or breathers to which it isconnected. Also, this arrangement permits axial adjustment of the jetnozzles in the discharge nozzles to vary the extent of vacuum producedthereby. It will :be understood that while in the illustrated embodimentfour guns are shown, any number can be employed according to the size ofmold cavity and other considerations, and that each device may serve anindividual breather or serve two or more breathers if practical to do soin individual molds.

The vacuum means contemplated for use in the present invention is farsimpler and less costly than the so-called full vacuum equipmentemployed in prior die casting machines. That is, the entire machine neednot be evacuated and it is not necessary to seal all leaks between theatmosphere and the mold cavity. Prior mold structures, employing theso-called flow vacuum means, have had the problem of the vacuum pullingthe metal completely into the runout passages and/ or vents. In thepresent invention, the novel breather construction obviates thisdifficulty.

Die casting, using the breather checking technique possible with thebreather and vacuum means of this invention, typically may follow thesesteps:

(1) Closing and lockup of die sections. (2) Actuating vacuum device anddevices and inspec- 8 tion of vacuum gage or gages to detect anymalfunctioning of the breathers. (3) Clean out any breather indicated asmalfunctioning. (4) Inject metal into mold cavity. (5) Open diesections, remove casting, and clean and lubricate cavity surfaces.

The foregoing recitation of steps assumes that the compressed air to thevacuum device will have been turned off after the checking procedure hasbeen completed. If, however, it is desired to maintain some degree ofvacuum in the die while the shot is being made, the air can, of course,be left on until the shot is completed and then turned off. At thispoint it is believed to be appropriate to point out still another reasonfor the use of the term breathers. When the vacuum device or devices arein use, air will, of course, be evacuated from the mold cavity to somedegree. When the vacuum device is turned off, the air will enter throughthe breathers and the mold cavity will be subjected to normalatmospheric pressure again by reason of the air being free to enterthrough the disabled vacuum device and passages thereof and of the dieto the breather bores.

The advantage of this procedure is that the operator is assured that themetal will fill the mold and breather cavities Without entrapment of airby the metal. The employment of vacuum while the shot is being made isusually advisable only where the area and thinness of the sections ofthe casting make it desirable to effect filling of the mold cavity withthe utmost rapidity to avoid the formation of cold shuts or kindreddefects. In general, however, it is sutficient to employ the vacuumdevice or devices merely to determine that no breather is notfunctioning correctly. Further, where so doing will improve the flowpattern, vacuum may be applied through less than all of the breathers ofa plural breather mold.

The spacing between the core ends 10 and 11" and the walls of apertures12' and 13' can be varied within limits not permitting the fiow of metaltherethrough to determine the rate of flow of air from the mold cavity,while the diameter of the core and aperture determines the volume of airreleased to the atmosphere during the casting operation. Variation inthis spacing in each breather attached to a given mold to exert adesired back pressure relative to the back pressure or pressures exertedby another breather or breathers incorporated in that mold. This willresult in the desired distribution or flow pattern of the casting metalwithin the mold cavity. Any number of breathers may be employed and, ofcourse, they are so located that the metal entering from the sprue '5will push the air and gases within the cavity towards the breathers. Foreach casting the breathers are located and are of such diameters andclearances and relative rates of flow and volume of air releasedtherethrough as to result in a desired flow pattern vvithin the mold.Where the breathers are located to form an opening in the casting, theycan be of any cross sectional configuration required. Otherwise thecircular configuration shown is the most practical to employ. The onlyessential is that suitable relative tapers be maintained between thebreather orifice forming components. Normally, this adjustment iseffected in the making of the molds, the cores being adjusted grindingaway the mounting shoulders or by inserting shims as test castingresults may indicate that a change in the relative axial positioning ofthe core in the mold is desirable. Also, while the channels connectingthe breather apertures with atmosphere may most readily be formed in thedie as shown, it will be realized that any other means, such as channelsor ducts formed wholly in the die or that the duct forming grooves maybe in the surface upon which the die is mounted as may be mostadvantageous for a particular mold. While certain presently preferredembodiments of the present invention have been shown and described, itwill be obvious to those skilled in the art that changes andmodifications may be made without departing from this invention. Forexample, the breather core and aperture may be rectangular or of a shapeother than circular; therefore, the aim in the appended claims is tocover all such changes and modifications as fall Within the purview ofthe invention.

I claim:

1. A mold for use in pressure die casting machines comprising a pair ofdies attachable one each to each of the elements constituting the diesupporting means of a die casting machine, portions adjacent faces ofsaid dies being shaped, when juxtaposed to define a mold cavity borderedby the meeting faces of said dies and said meeting faces beinginterrupted only by a sprue hole formed in the said meeting faces ofsaid dies for the conduct of molten metal into the mold cavity, meansfor permitting the expulsion of air and gases from the mold cavityincident to the entry of molten metal into the mold cavity; said meanscomprising at least one breather aperture extending through one of saiddies from the mold cavity surface toward the face of said one die whichis in contact with the machine element on which it is supported andmeans disposed on the other of said dies to project into said breatheraperture when said dies are juxtaposed to form said mold cavity and tocooperate with the wall surface of said breather aperture at a pointthereon spaced from said mold cavity to form a narrow orifice throughwhich air and gas can flow but through Which the molten metal, by reasonof the viscosit thereof, cannot flow, and other means affordingcommunication between the end of said breather aperture remote from saidmold cavity with atmosphere.

2. A die casting mold as claimed in claim 1 in which said breatheraperture extends to the face of said one die opposite the face whichengages the other die and in which the interengaging faces of said onedie and of the portion of the machine element to which said one die issecured are shaped to form at least part of said means affordingcommunication between said one end of said breather aperture withatmosphere.

3. A die casting mold as claimed in claim 1 in which said breatheraperture from the juncture thereof with said mold cavity surface to saidorifice is of decreasing diameter and in which said means cooperatingtherewith to form said orifice comprises a core member disposed in theaxial line of said breather aperture and projecting into said breatheraperture when said dies are juxtaposed to form said mold cavity; saidcore member within said cavity being also of decreasing diameter towardsaid orifice but at a lesser included angle than the taper of saidbreather aperture and combining with said breather aperture to form saidorifice at said point in said breather aperture remote from said moldcavity.

4. A die casting mold as claimed in claim 1 in which said one of saiddies is provided with a plurality of said breather apertures in whichthe other of said dies is pro vided with a corresponding plurality ofcooperating, orifice forming means, and in which said one die isprovided with a single means cooperating with a surface of the machineelement on which said one die is mounted to afford communication betweenall of the ends of said breather apertures remote from said mold cavityand atmosphere.

5. A die casting mold as claimed in claim 1 in which said one of saiddies is provided with a plurality of said breather apertures and theother of said dies is provided with a corresponding plurality ofcooperating, orifice forming means, and in which said one die isprovided With a plurality of said other means cooperating with a surfaceof the machine element on which said one die is mounted to affordcommunication between the ends of said breather apertures remote fromsaid mold cavity and atmosphere, at least one of said communicationaffording means serving one only of said plurality of breatherapertures.

6. A die casting mold as claimed in claim 1 in which said other meansaffording communication between said end of said breather apertureremote from said die cavity and atmosphere includes a hole in a side ofsaid one die adjacent to the face thereof opposite the face whichengages said other die.

*7. A die casting mold as claimed in claim 3 in which said core memberserves additionally to cause the casting to be stripped from said onedie upon separation of the dies for removal of the casting.

'8. A die casting mold as claimed in claim 4 in which said meansaiford'ing communication between said ends of said breather aperturesremote from said mold cavity and atmosphere includes a single hole in aside of said one die adjacent to the face thereof opposite the facewhich engages said other die.

9. A die casting mold as claimed in claim 5 in which said meansaffording communication between said ends of said breather aperturesandatmosphere includes a plurality of holes in the side surface of saidone die at least one of said hole-s being connected to affordcommunication between said end of one only of said breather aperturesand atmosphere.

10. A mold {for use in pressure die casting machines comprising a pairof dies attachable one each to each of the opposed and relatively movingelements constituting die supporting means of a die casting machine,portions of the adjacent faces of said dies being shaped when juxtaposedto define a mold cavity bordered by the meeting faces of said dies andsaid meeting faces being interrupted only by a sprue hole formed in thesaid meeting faces of said dies for the conduct of molten metal into themold cavity, means for permitting the expulsion of air and gases fromthe mold cavity incident to the entry of molten metal into the moldcavity; said means comprising at least one breather aperture extendingthrough one of said dies from the mold cavity surface toward the face ofsaid one die which is in contact with the machine element on which it issupported and means disposed on the other of said dies to project intosaid breather aperture when said dies are juxtaposed to form said moldcavity and to cooperate with the wall surface of said breather apertureat a point thereon spaced from said mold cavity to form a narrow orificethrough which air and gas can flow but through which the molten metal,by reason of the viscosity thereof, cannot flow, other means affordingcommunication between the end of said breather aperture remote from saidmold cavity with atmosphere, and a pneumatic jet pump device having theintake port thereof connected to said other means effective to evacuateair from said breather aperture and said mold cavity while the jet meansof said pump device is in operation.

11. A die casting mold as claimed in claim 10 in which said jet pumpdevice includes a vacuum gauge for indicating the extent of evacuationeffected by said jet pump device.

12. A die casting mold as claimed in claim 10 in which said one of saiddies is provided with a plurality of said breather apertures and saidother die is provided with a corresponding plurality of cooperating coremembers, and in which said other means affords communication betweensaid ends of all of said breath-er apertures and atmosphere.

13. A mold for use in pressure die casting machines comprising a pair ofdies attachable one each to each of the opposed and relatively movingelements constituting the die supporting means of a die casting machine,portions of the adjacent faces of said dies being shaped, whenjuxtaposed, to define a mold cavity bordered by the meeting faces ofsaid die-s and said meeting faces being interrupted only by a sprue holeformed in the said meeting faces of said dies for the conduct of moltenmetal into the mold cavity, means for permitting the expulsion of airand gases from the mold cavity incident to the entry of molten metalinto the mold cavity; said means comprising a plurality of breatherapertures extending through one of said dies from the mold cavitysurface thereof toward the face of said one die which is in contact withthe element on Which it is supported in the machine and a correspondingplurality of means disposed on the other of said dies and arranged toproject into said breather apertures when said dies are juxtaposed toform said mold cavity and to cooperate with the wall surfaces of each ofsaid breather apertures at a point thereon spaced from said mold cavityto form narrow orifices through which air and gas can flow but throughwhich the molten metal, by reason of its viscosity, cannot flow, aplurality of other means each affording communication between at leastone of said ends of breathers and atmosphere, and a plurality ofpneumatic jet pump devices each having the intake port thereof connectedto one each of said other means; said jet pump devices beingindependently operative, upon activation, to evacuate air from the moldcavity through the breather aperture or apertures to which the device isconnected by said other means.

14. A mold for use in pressure die casting machines comprising a pair ofdies attachable one each to each of the relatively movable elementsconstituting the die supporting means of a die casting machine, theadjacent faces of said dies being shaped, when juxtaposed, to define amold cavity bordered by the meeting faces of said dies and said meetingfaces being interrupted only in a sprue hole formed by the said meetingfaces of said dies for the conduct of molten metal into the mold cavity,and breather aperture means extending from said mold cavity through oneof said dies and effective to permit the expulsion of air and gas fromsaid mold cavity incident to the injection of molten metal; saidbreather means including components carried by each of said diesoperative upon closing of said dies to form a narrow orifice remote fromsaid mold cavity through which air and gas can flow but through whichthe molten metal, by reason of its viscosity cannot flow, and othermeans at the side of said orifice remote from said mold cavity affordingcommunication between said breather aperture means and atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS981,438 Link Ian. 10, 1911 1,960,992 During May 29, 1934 2,061,765 GuyotNov. 24, 1936 2,799,066 Federman et a1. July 16, 1957 3,070,857 VenusIan. 1, 1963 FOREIGN PATENTS 339,721 Great Britain Dec. 18, 1930

1. A MOLD FOR USE IN PRESSURE DIE CASTING MACHINES COMPRISING A PAIR OFDIES ATTACHABLE ONE EACH TO EACH OF THE ELEMENTS CONSTITUTING THE DIESUPPORTING MEANS OF A DIE CASTING MACHINE, PORTIONS ADJACENT FACES OFSAID DIES BEING SHAPED, WHEN JUXTAPOSED TO DEFINE A MOLD CAVITY BORDEREDBY THE MEETING FACES OF SAID DIES AND SAID MEETING FACES BEINGINTERRUPTED ONLY BY A SPRUE HOLE FORMED IN THE SAID MEETING FACES OFSAID DIES FOR THE CONDUCT OF MOLTEN METAL INTO THE MOLD CAVITY, MEANSFOR PERMITTING THE EXPULSION OF AIR AND GASES FROM THE MOLD CAVITYINCIDENT TO THE ENTRY OF MOLTEN METAL INTO THE MOLD CAVITY; SAID MEANSCOMPRISING AT LEAST ONE BREATHER APERTURE EXTEND-